History of aicraft piston engines

The fuel valve was then opened until firing restarted

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Unformatted text preview: tia of the rotating engine, it was possible to adjust t o the appropriate mixture by trial, without danger of stalling the engine. W ith a known setting of the valves for idling, after the engine had been s tarted the air throttle was opened wide, at which time firing ceased but r otation continued. The fuel valve was then opened until firing restarted and m aximum propeller speed was attained. Because the reverse process was difficult, throttling down was accomplished by temporarily cutting the i gnition, and the engine was kept going by short bursts of power. Oddly e nough this technique was easy to learn and pilots seemed to like it. 25 I mportant engines of 1909 included the following (see also table 1, p . 8 8). Wright Curtiss Antoinette ENV Darracq Gnome Renault R EP Anzani 4- and 6-cylinder vertical, water cooled 8-cylinder V-type, water cooled 8 -and 16-cylinder V-type, water cooled 8-cylinder V-type, water cooled 2-cylinder opposed, water cooled 7-cylinder rotary, air cooled 8-cylinder V-type, air cooled 7-cylinder fan, air cooled 3-cylinder fan, air cooled T hese engines accounted for n early all important flights in 1909, including t he winners of the first official aviation contests at R heims. T he Darracq engine, used by Santos-Dumont, was important for b eing one of the first aircraft engines to use mechanically operated inlet valves. The JAP (J. A. Prestwich Co.) motorcycle engine used by A. V. Roe i n his early airplane appears to have been the only other one using such valves. All other aircraft of the period used automatic inlet valves, opened by suction. Since automobile engines had been using mechanically operated valves for many years before 1909, it is hard to understand, why this i mportant feature was so late in coming into use for aircraft engines. 26 Engines 1910-1918 T he period 1910-1918, which included World War I, saw such rapid d evelopments of aircraft engines that only the important ones can be d escribed here. By " important" I m ean those which pioneered successful n ew design features or which were particularly notable in service. E arly in this period the Gnome air-cooled rotary engine was dominant and was built in many countries and in several modified designs, i ncluding models by LeRhone and Clerget (French) the Bentley B R-1 a nd BR-2 (British) and the Oberiirsel and Siemens (German). It reached its maximum development early in the war and was definitely obsolescent by 1918. Reasons for its demise were chiefly a limitation on speed due to centrifugal stress, the considerable windage losses, design limitations imposed by rotation of all parts but the crankshaft, and a rather strong gyroscopic effect on the airplane during turns. It set a pattern, however, for the later development of the modern air-cooled radial engine. It was a f orged-and-machined-all-over e ngine, and it was radial and air-cooled, features which are now characteristic of most large aircraft piston engines. O ther rotary engines were built at this time, but none achieved the i mpo...
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This document was uploaded on 01/19/2014.

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